Polychlorinated Compounds biphenyls

Polychlorinated Compounds Polychlorinated dioxins (PCD) Polychlorinated biphenyls (PCB) Industrial production or by-products, landfills, incinerators. 

Sequential photocyanation has been achieved in aqueous MeCN for a variety of polyhaloaromatic compounds, including polychlorinated benzenes, biphenyls, naphthalenes, and dioxins. These reactions involve the triplet state and show a low degree of regioselectivity. The mechanism was rationalized as involving a Sn2At path with an autoacceleration of the reaction due to the higher susceptibility to further nucleophilic substitution of the products formed in each step (see Scheme 4.20) [123,124],... 

Many commercial products are complex chemical or physical mixtures. In some cases the use of the type of search scheme described above is not always useful. Sometimes, all that is required is a broad based characterization or a generic identity in terms of a product type. A good example is a polychlorinated biphenyl (a PCB), such as the Arochlor 1254 shown in Figure 8. This time the identification of the individual component polychlorinated compounds would not be useful. Therefore in this case a normal absolute scoring scheme is preferred where the material is treated as a single entity. The computer interpretation (Table 6) accurately classifies the sample as an aromatic material with multiple halogen (ring) substituents. 

Fig. 1. Structures of polycyclic compounds, (a) Polychlorinated (brominated) biphenyl (b) Polychlorinated (o-, m-, p-) terphenyl (c) Polychlorinated naphthalene (d) Polychlorinated dibenzofuran...

Ei ivironrr lent Absence of toxic compounds such as polychlorinated biphenyls (PCB s)... 

Solvent extraction followed by gas chromatographic analysis is used to determine paraffin wax antioxidants (qv), ie, butylated hydroxyanisole and butylated hydroxytoluene and other volatile materials. Trace amounts of chlorinated organic compounds, eg, polychlorinated biphenyls, can be deterrnined by using a gas chromatograph with an electron-capture detector (22). 

Common examples of compounds that are amenable to carbon adsorption are aromatics (benzene, toluene) and chlorinated organics (trichloroethylene, trichloroethane [71-55-6, 75 -(9(9-j5y, tetrachloroethylene, polychlorinated biphenyls (PCBs), DDT /T(9-77-77, pentachlorophenol [87-86-5J. Compounds that are not adsorbed effectively by carbon include ethanol [64-17-5], diethylene glycol [111-46-6], and numerous amines (butylamine [109-73-9, 13952-84-6, 75-64-9], triethanolamine [102-71-6], cyclohexylamine [108-91-8], hexamethylenediamine [108-91-8] (1). Wastewater concentrations that are suitable for carbon adsorption are generally less than 5000 mg/L. 

SW-846, is used to measure emissions of semivolatile principal organic constituents. Method 0010 is designed to determine destruction and removal efficiency (DRE) of POHCs from incineration systems. The method involves a modification of the EPA Method 5 sampling train and may be used to determine particulate emission rates from stationary sources. The method is applied to semivolatile compounds, including polychlorinated biphenyls (PCBs), chlorinated dibenzodioxins and dibenzofurans, polycyclic organic matter, and other semivolatile organic compounds. 

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) ai e toxic compounds of anthropogenous origin, able to accumulate in tissues of alive organisms and to cause different diseases. These compounds ai e the most dangerous for aquatic ecosystems as they easily adsorb in sludge and ai e included in food chains of biota. Humans consume PCBs and OCPs mostly with fish. 

It is known that the brain is one of the most sensitive sites of action of steroids in utero, and recently there have been suggestions that EDs may affect normal brain development and behaviour. For example, it has been alleged that in utero exposure to polychlorinated biphenyl compounds (PCBs) resulted in adverse effects on neurologic and intellectual function (memory and attention) in young children born to women who had eaten PCB contaminated fish in the USA." It has also been speculated that exposure to environmental pollutants with steroidal activity may be infinencing human sexual development and sexually controlled behavioiir." ... 

Those man-made chemicals which have been identified as being oestrogenic belong to several major groups of chemicals including organochlorine pesticides, polychlorinated biphenyls, alkylphenolic compounds, ... 

Extraction, employs a liquid solvent to remove certain compounds from another liquid using the preferential solubility of these solutes in the MSA. For instance, wash oils can be used to remove phenols mid polychlorinated biphenyls (PCBs) from die aqueous wastes of synthetic-fuel plants and chlorinated hydrocarbons from organic wastewater. 

Liver cancer can also be a consequence of exposure to hepatotoxic chemicals. Natural hepatocarcinogens include fungal aflatoxins. Synthetic hepato-carcinogens include nitrosoamines, certain chlorinated hydrocarbons, polychlorinated biphenyls (PCBs), chloroform, carbon tetrachloride, dimethyl-benzanthracene, and vinyl chloride.Table 5.15 lists the chemical compounds that induce liver cancer or cirrhosis in experimental animals or... 

Polychlorinated biphenyls (PCBs) Highly toxic organic compounds used in the electrical industry, use of w hich is now restricted. 

The values of n and the corresponding N which are necessary to resolve 50-90% of the constituents of a mixture of 100 compounds are listed in Table 1.5, thus making clear the limitations of one-dimensional chromatography. For example, to resolve over 80 % of the 100 compounds by GC would require a column generating 2.4 million plates, which would be approximately 500 m long for a conventional internal diameter of 250 p.m. For real mixtures, the situation is even less favourable to resolve, for example, 80 % the components of a mixture containing all possible 209 polychlorinated biphenyls (PCBS) would require over lO plates. 

R. M. Kinghorti, P. J. Marriott and M. Cumbers, Multidimensional capillary gas chr O-matography of polychlorinated biphenyl marker compounds , 7. High Resolut. Chromatogr. 19 622-626 (1996). 

In general, capillary gas chromatography provides enough resolution for most determinations in environmental analysis. Multidimensional gas chromatography has been applied to environmental analysis mainly to solve separation problems for complex groups of compounds. Important applications of GC-GC can therefore be found in the analysis of organic micropollutants, where compounds such as polychlorinated dibenzodioxins (PCDDs) (10), polychlorinated dibenzofurans (PCDFs) (10) and polychlorinated biphenyls (PCBs) (11-15), on account of their similar properties, present serious separation problems. MDGC has also been used to analyse other pollutants in environmental samples (10, 16, 17). 

Figure 13.1 Monitor (FID) (a) and analytical (ECD) (b) channel responses for PCB congeners in Aroclor 1254, showing selection of the six heart-cut events Frr-st columns, HT8 second columns, BPX5. Reprinted from Journal of High Resolution Chromatography, 19, R. M. Kinghorn et al., Multidimensional capillar-y gas chr omatography of polychlorinated biphenyl marker compounds , pp. 622-626, 1996, with per-mission from Wiley-VCH.

Dioxins are prominent members of the class of polychlorinated hydrocarbons that also includes diben-zofuran, biphenyls and others. Dioxins are highly toxic environmental contaminants. Like others small planar xenobiotics, some dioxins bind with high affinity to the arylhydrocarbon (Ah) receptor. Dioxins activate the receptor over a long time period, but are themselves poor substrates for the enzymes which are induced via the Ah-receptor. These properties of the dioxins and related xenobiotics may be important for the toxicity of these compounds. Dioxins like 2,3,7,8-tetrachloro-p-dibenzodioxin can cause persistent dermatosis, like chloracne and may have other neurotoxic, immunotoxic and carcinogenic effects. 

Nebeker, A.V., Puglisi, E.A., and Defoe, D.L. (1974). Effect of polychlorinated biphenyl compounds on survival and reproduction of fathead minnow and llagfish. Transactions of the American Fisheries Society 103, 562-568. 

There is a vast range of aqueous organic pollutants with a wide toxicity profile. Some, e.g. polychlorinated biphenyls, certain herbicides, fungicides and pesticides, and organo-mercury compounds, are persistent and may bioaccumulate in the food chain. Trace contaminants such as sodium chloride, iron and phenols (especially if chlorinated) may also impart a taste to water. Typical consent levels for industrial discharges are provided in Table 13.10. 

Heavy metals may also be concentrated in passage up the food chain. Other pollutants, e.g. fungicides, pesticides, biocides, polychlorinated biphenyls or organic mercury compounds, are persistent and can therefore also bioaccumulate. 

Gilbert ES, DE Crowley (1997) Plant compounds that induce polychlorinated biphenyl degradation by Arthro-bacter sp. strain BIB. Appl Environ Microbiol 63 1933-1938. 

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